Method of making coupler dispersions



Patented June 4,1946

' METHOD OF MAKING COUPLER DISPERSIONS Richard V. Young, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation oi New Jersey NoDrawlng. ApplicationMay 27, 1944,

Serial No. 537,726

9 Claims.

. This invention relates to color photography and particularly to the incorporation of color-' forming compounds in photographic emulsions.

The incorporation of silver or other metallic salts of couplers in silver halide emulsions has been described in Peterson U. S. Patents 2,296,306, granted September 22, 1942, and 2,353,754 granted July 18, 1944'. According to the methods described in these patents, the cou pler is added to the emulsion before or after precipitation of the silver halide, and the silver salt of the coupler is formed by' replacement of a sodium or other solubilizing atom in the coupler with a silver atom or other metallic atom which renders the coupler insoluble. According to the prior methods, it is impossible to increase the coupler concentration above about 0.02 to 0.025 molar andthe gelatin concentration above about 1 per cent unless coarse-grained emulsions are used. Higher coupler concentrations cause 'the dispersion to. coagulate and higher gelatin concentrations cause the gelatin solution to set to a solid mass that cannot be remelted at any reasonable temperature.

It is, therefore, an object of the present invention to provide a method for increasing-the coupler concentration in dispersions of metallic salts of couplers in gelatin. A further object is to provide a methodrior increasing the gelatin concentration in such dispersions.

other metallic salt of the color former, an aliphatic amine or an amino acid. A soluble salt of the amino acid'may be used if the acid is not sufliciently soluble.

The emulsion containing. the silver salt of the color former is made by forming the sodium or other soluble salt of the color former in water and adding it ,directlyto the final emulsion or to a separate portion of emulsion which is then mixed with the final emulsion. The silver salt oi the coupler is formed at once when the sodium salt is mixed with the silver halide emulsion. It is also possible to form the salt of another metal, such as cadmium, which is insoluble and add it to the silver halide emulsion.

The couplers which I employ contain lmino or mercapto groups or substituted mercapto groups, which are capable of formation of a silver salt or silver complex. These couplers may contain the heterocyclic structure described in Peterson U. S. Patents 2,296,306 and 2,353,754, or

. 2 the thioglycolic structure described! in Weissberger, Kibler and Young U. S. application Ser.

No. 539,780 filed June 10, 1944. The following couplers are suitable for forming cyan, magenta, and yellow dyes respectively:

cmQwncocmsn Z-thioglycolylamino-4-chloro fi-methylphenol H 0 C-NH(OCH1SH O=C #1 N l ll l-phcnyl-S-thioglycolylamino-fi-pyrazolone p-M-honzoylacotaininolbenzcnc-sulfam idothliophenol According to the present invention, an aliphatic amine, especially a lower aliphatic amine, or an amino acid is added-to the emulsion in which the silver salt of the coupler is produced or to the. solution of the couplerbeifore formation of the silver salt. 7 This makes it possible to increase by two or three times the concentration of the coupler which may be incorporated in the emulsion without flocculation. Similarly, the gelatin concentration of the emulsion may be increased to 3 or ,4 per cent with fine-grain emulsions, and the emulsion may be remelted at reasonably low-temperatures. In general, it may be said that the use of these organic amines or amino acids decreases the effect which the silver salts of the couplers have upon la in.

Aliphatic amines which may be employed according to my invention include ethylamine, diethylamine, propylamine, n-butylamine, ethanol-- amine and diethanolamine. Amino acids include glycine, a-aminobutyric acid, a-aminocaproic acid, e-aminocaproic acid, a-amlnocapryllic acid, phenylglycine, s-am'inoethylsulfonic acid and hydrolyzed gelatin. Tertiary amines and aromatic primary .or secondary amines may be used but are less effective than the preferred types.

The concentration of the amine or amino acid may vary over a wide range but the quantities preferably used are from one to two equivalents of the amine or amino acid per mole of coupler. My invention will be further illustrated by reference to the following example which describes a typical preparation of a color-forming emulsion according to my invention:

A coupler solution is prepared by dissolving 9.3 grams (0.04 mole) of 2-thioglycolylamino-4- chloro-5-methylphenol in 160 cc. of 2% sodium hydroxide. A very fine grain silver chloride emulsion is prepared containing 8.6 grams (0.06 mole) of silver chloride in 740 cc. of 7% gel solution. To this is added with thorough mixing 100 cc. of a solution containing 12.2 grams (0.08 mole) of sodium salt of e-amino caproic acid. The coupler solution is added to this with rapid stirring and after a few minutes of mixing the dispersion is refrigerated.

" The dispersion may be remelted at any time and before coating is mixed with 1 liter of a high speed light-sensitive silver halide emulsion, which may be color-sensitized or unsensitized as required by the nature of the color process.

My method of preparing the dispersions of silver salts of couplers has several important advantages. Because of the increased coupler con centration in the emulsion, a higher dye density can be obtained than was heretofore possible. Because of the increased gelatin concentration, the emulsion contains less water and therefore can be coated directly on subbed film support. Furthermore, the higher gelatin concentrations allow the dispersions to be set, washed and remelted by a technique that is regularly used in the preparation of photographic emulsions. It will be understood that the examples and modifications described herein are illustrative only and that my invention is to be taken as limited only b the scope of the appended claims.

I claim:

1. The method of increasing the concentration of coupler compound in a color-forming photographic emulsion, which comprises forming an insoluble metallic salt of a coupler compound selected from the class consisting of coupler compounds containing imino, mercapto and acyl-substituted mercapto groups, in a silver halide emulsion in the presence of an amino compound selected from the class consisting of aliphatic amines and amino acids.

2. The method of increasing. the concentration of coupler compound in a color-forming photographic emulsion, which comprises forming a silver salt of a coupler compound selected from the class consisting of coupler compounds containing imino, mercapto and acyl-substituted mercapto groups, in a silver halide emulsion in the presence of an amino compound selected from the class consisting of aliphatic amines and amino acids.

3. The method of increasing the concentration of coupler compound in a color-forming photographic emulsion, which comprises forming a silver salt of coupler compound selected from the class consisting of coupler compounds containing imino, mercapto and acyl-substituted mercapto groups, in a gelatino-silver halide emulsion in the presence of an. appreciable amount of an aliphatic amine.

4. The method of increasing the concentration of coupler compound in a color-forming photographic emulsion, which comprises forming a silver salt of a coupler compound selected from the class consisting of coupler compounds containing imino, mercapto and acyl-substituted mercapto groups, in a gelatino-silver halide emulsion in the presence of an appreciable amount of silver salt of a coupler compound selected from the class consisting of coupler compounds containing imino, mercapto and acyl-substituted mercapto groups, in a gelatino-silver halide emulsion in the presence of an amount of amino acid at least equivalent to the amount of coupler in the emulsion. I

7. The method of increasing the concentration of coupler compound in a,|c0101'f0;.miIlg photographic emulsion, which comprises forming a silver salt of a coupler compound selected from the class consistin of coupler compounds containing imino, mercapto and acyl-substituted mercapto groups, in a gelatino-silver halide emulsion in th presence of approximately one mole of a lower aliphatic amine per mole of coupler in the emulsion.

8. The method of increasing the concentration of coupler compound in a color-forming photographic emulsion, which comprises forming a silver salt of a coupler compound selected from. th class consisting of coupler compounds containing imino, mercapto and acyl-substituted mercapto groups, in a gelatino-silver halide emulsion in the presence of approximately one mole of an amino acid per mole of coupler in the emulsion.

9. The method of producing a color-forming photographic emulsion, which comprises forming a sensitive silver salt in a colloidal material and then incorporatin in said material a solution of (1) a coupler compound containing a group selected from the class consisting of imino groups, mercapto groups, and acyl-substituted mercapto .groups, ,said groups containing a group replace- RICHARD V. YOUNG. 

